Modulating reflectors for controlling the rate of change of sound emission



April 3, 1928.

, J. H. HAMMOND. JR MODULATING REFLEGTORS FOR CONTROLLING THE RATE OF CHANGE OF SOUND EMISSION Filgd Jan. 28. 1 5 Sheets-Sheet 11..

April 3, 1928. 1,664,556

J. H. HAMMOND, JR

MODULATING REFLECTORS FOR CONTROLLING THE RATE OF CHANGE OF SOUND EMISSION 3 Sheets-Sheet 2 Filed Jan. 28. 1926 EN hi k xbw MIMI Evy

April 3, 1928. 1,664,556

J. H.- HAMMOND, JR MODULATING REFLECTORS FOR CONTROLLING THE RATE OF CHANGE OF SOUND EMISSION 19 3 Sheets-Sheet 55 Filed Jan. 28.

Patented Apr. 3, 1928.

UNITED STATES PATENT OFFICE.

JOHN HAYS HAMMOND, JR, OF GLOUCESTER, MASSACHUSETTS.

MODULATING BEFLEOTORS FOR CONTROLLING THE RATE OF CHANGE OF SOUND EMISSION.

Application filed January 28, 1928.

June 1923, published by Henry Holt & Com-.

pany, New York, there is shown an intensity curve such as would be produced if every equal increment in the outer stimulus produced an equal increment in the intensity of the sensation. Such a straight line curve may be considered as an ideal curve for sensation stimuli. It has been found, however, by experimental investigations in psychology that the average natural relation between sensation and stimuli follows in general a law said to have been discovered and formulated by G. T. Fechner and commonly known as \Vebcrs law. In The Elements of Scientific Psychology by Knight Dunlap, edition of 1923, published by C. V. Mosby Company, St. Louis, on page 125 VVebers law is stated as follows:

The intensity difference threshold expressed as a ratio (or percentage), is approximately constant for changes in intensity of stimulation alone, throughout a certain limited range of intensities.

Vebers law is also shown graphically in the work by James referred to in Figure 2, page 18.

It is one of the principal objects of the present invention to provide improved means for pianofortcs for modifying the variation in intensity of sound inversely with respect to the average natural relation between sensation and stimuli.

According to the present invention the modification of the intensity variations is such that this non-linear relationas indicated by the curve of IVebers law referred tois compensated for sufliciently to make the apparent relation one of even and proportional gradations, in other words a linear relation, such as the ideal curve.

According to this feature of the invention,

Serial No. 84,274.

therefore, increments of tone are thus con trolled in such manner as to render the variations in intensity effective to the average listener to an increased degree, thus producing more satisfactory expression, and more intense dynamic effects, in the music.

Other objects will appear from the following description taken in connection with the accompanying drawings in Which Figure l is an elevation partly in section of one form of musical instrument embodying features of the invention;

Figure 2 is a bottom plan view of the mechanism shown in Figure 1;

Figure 3 is a curve showing the relation between the movements of certain elements of the mechanism of Figure 1;

Figures 4, 5, 6, and 7 are .end views of several forms of the sound control mechanism of Figure 1; and

Figure 8 is a graphic representation of the openings of the devices of Figures 1, 4, 5, 6 and 7 respectively.

Like reference characters refer to like parts in the several figures of the drawings.

In the following description and claims, parts will be identified by specific names for convenience of expression, but they are intended to be as generic in their application to similar parts or the equivalent construction as the art will permit.

Referring to the drawings, there is shown so much of a grand piano 10 as is necessary to an understanding of the present invention and having applied thereto the features of the present invention. The embodiment illustrated is provided with a plurality of strings such as 11 for producing damped compressional waves, which are tuned to the notes of the musical scale in accordance with well-known practice. It will be understood that there may be provided for each note of the musical scale, one or more of such strings as may be desired. The strings 11 are mounted in any desired way by conventional means, such means being well known and requiring no further description. Located below the strings is a sounding board 12 for vibrating the strings of each of the notes of the scale by percussion, there is provided a suitable hammer action such as 13 operatively connected to one of the keys 14 of the manual.

Below the manual and secured to a portion oi the frame work of the instrument,

there is provided a pedal block 15., upon which there is positioned a plurality of pedals shown three in number as at 16, 17 18. The two right hand pedals, as seen in Figure 1, designated respectively 17, 16, are connected to the susteuuto and loud pedal actions of the pin-ac in a conventional manner and having no bearing on the present invention need not be further described.

The-left hand pedal 18 is operatively connected to reciprocate a vertical rod 20, the upper end of which engages one arm of a bell crank lever 21 pivoted as at 22 to lined portion of the instrument. The other arm of the bell crank lever 21 is pivotally connected by means of a connecting rod 23 to one arm of a second bell crank lever 24 which is pivoted as at 25 to rotate in a plane at an angle to the plane oi rotation of the first bell crank lever 21. The other arm of the second bell crank lever 24 is pivotally connected to a link 26, the other end of whicn is pivotally connected to an intermediate portion of a lever 27 secured to a rotatable shaft 28. The outer or free end of the lever 27 is pivotally connected by means of a connecting link 29 to a reciprocating connecting rod 30. Secured tothe rod 23 is a collar 31 to which is attached a spring 32 the other end of which is fastened to a bracket The shaft 28 is journalled in spaced bearings mounted in the casing of the piano and extends from the casing to the upper portion of the piano as indicated in Figure 1. The shaft 28 is provided with a fixed collar 35 thereon for maintaining the shaft in fixed longitudinal position with respect to its bearings, an arm 86 is ailined to the shaft near the upper wall oi the casing, and the outer end of the arm is pivotally connected by means of a connecting link '37 to an upper reciprocating connecting rod 38.

The casing of the instrument is provided with oppositely disposed controllable apertures as at 40 (see Figure l) and ll (see Figure 2).

Mounted in the upper aperture 40 is a series of undulating reflectors as at 42 serving to control the emission of sound. Each reflector 42 is preferably in the form oi an elongated flat member mounted to rotate about its longitudinal axis. The edges of the reflectors are so formed that when the re ilectors are closed the openings are wholly closed, but that when the reflectors are rotated the opening is increased to a desired extent, and the cooperating edges are to med so that the rate of opening is gradual. Each reflector is provided on its outer "face with an arm as, the outer end of which is pivotally connected to the upper connecting rod. 38.

In the lower aperture All of the casing there is mounted a second series of reflectors to control the emission of sound. The con struction of the lower group of reflectors corresponds to that of the upper group and it is thought that further description thereof is therefore not necessary. The outer ends of the arms as of the reflectors of the lower group are pivotally connected to the lower connecting rod 30. Surrounding each of the apertures the casing includes an upper wall 45, and a lower wall 46 skirting the respective apertures and having the edge shaped to conform to the edge of tie contiguous reflector as.

In operation the manual of the piano is employed by the musician in the usual way to cause vibration of the strings 11 in accordance with the music being played. The musician controls with one foot the left hand pedal 18 to modify or modulate the tone emitted from the instrument as may be de-' sired. Downward movement of the forward end of the pedal 18 causes movement of the rod 20 upwardly and a movement of the bell crank lever 21 in a counter clockwise direction as seen in Figure 1. This in turn moves the rod 23 towards the left and causes the rotation of the bell crank lever 2a in a counter clockwise direction as seen in Figure 2. The motion of the bell crank lever 24: is transmitted by means oil the link 26 to the lever 27 thus moving the link 29 and the rod 30 towards the right (see Figure 2), and also rotating the shaft 28 and the upper arm 36 so as to move the link 37 and the upper rod 38 towards the right (see Figure 1).

The bell crank lever 2d, the link 26 and the lever 27 form collectively a speed changing mechanism whereby a constant speed of movement of the pedal 18 is converted into a variable speed movement of the rods 30 and 38. The relativity of the movement of the pedal 18, assuming it to he constant in speed, and of the resultant movements of the rods 30 and 38 is indicated. graphically in Figure 3, the abscissa of which is calibrated to represent the angular movement of the pedal 18, and the ordinate, the corresponding distance through which the rods 38 and 30 are moved. A curved line 50 indicates that the initial downward movement of the forward end of the pedal 18 produces relatively fast movement of the rods 38 and 30, but that continued downward movement of the pedal 18 produces decelerated movement of the rods.

A curved line 51 is also shown indicating the relative motion of the parts when the bell crank lever 24, the link 26 and the lever 2'? are so proportioned as to produce a constant ratio 01 speed. One form of transmission mechanism which may be employed in place of the mechanism herein shown and described is disclosed in my copending application Serial No. 753,558, filed December 3rd, 192% for piano shutter.

ill)

lit

Referring now to Figure 4 there is shown on an enlarged scale an end view of a mod ulating reflector of the type disclosed in the said co-pending application and having contiguous edges bevelled as at 52. Each reflector is pivotally mounted on its longitudinal axis 53 for rotation from the closed position indicated in Figure l into desired open position. The effect of using the modulating reflector of Figure 4 in combination with a motion transmitting mechanism of the type disclosed in said prior application whereby the speed ratio is maintained uniformly, is indicated graphically by the curve 5% of Figure 8. In this curve the abscissa represents equal means of motion of the foot pedal 18 and the ordinate represents the area of opening between the reflectors. It will be seen from this curve that the openingincreases rapidly as the reflectors are moved from their closed position and that the area of opening then increases in substantially a straight line ratio, but tapering off to a decreased ratio towards the end of the movement. As the intensity of sound emitted from the instrument would be expected to be substantially proportional to the area of opening it will be seen that when the reflector-s are only slightly opened a very large change in intensity is produced. From a psychological standpoint it has been shown from the foregoing consideration of WVebers law that rapid changes in intensity with small volume are unnecessary to produce. desired effects when the volume of sound is small, and furthermore that the tapering ofl' referred to is also undesirable.

In Figure 5 there is shown another modi fied form of modulating reflector having a bevelled edge partially curved as at 55 and having the outer end cut off as at Each reflector is pivotally mounted on its longitudinal axis as at 57 so as to be rotatable from the closed position as shown in Figure 5 into desired open position. The efi'ect of opening the modulating reflector of Figure 5, by means of a motion transmitting mechanism of the uniform ratio type as disclosed in the said prior application, is indicated graphically by a curve 58 in Figure 8. It will be seen from this curve that the opening is relatively gradual at the start but increases rapidly and tapers off toa lesser degree than the curve 54.

Figure 6 shows an enlarged end view of the modulating reflector 42 of Figures 1 and 2. The effect of using this form of modulating reflector in combination with a motion transmitting mechanism of the type in which the speed ratio is maintained uniform is in-. dicated by a curve 59 in Figure 8. It will be seen from this curve that the area of opening is more gradually increased at the beginning and that subsequently a more rapid opening is obtainable, with the final area of opening relatively larger than that provided by the forms shown in Figures at and 5.

In Figure 7 there is shown another modified form of reflector mounted for rotation on its longitudinal axis 60. The effect of using the modulating reflector of Figure 7 in combination with a motion transmitting mechanism of the type in which a speed ratio is maintained uniform is shown by a curve 61 of Figure 8. It will be seen from this curve that the increase in opening is very gradual. during the first third of the movement of the pedal 18, after which the opening is increased more rapidly but that the final opening is notas large as that given by the other types already shown.

The present disclosure has reference to a modulating reflector of the type shown in Figure-6, giving the largest maximum open ing and therefore the greatest volume of sound, used in combination with the variable speed motion transmitting mechanism'shown in Figures 1 and 2 and hereinbefore described. The effect thus obtained is shown graphically by a curve 62 in Figure 8. It is seen from this curve that the increase of area of opening is extremely gradual at first, and then increases rapidly, and finally assumes a value as great as that shown by' the curve 59.

As the volume of sound may be considered as being substantially proportional to the area of opening it will be understood that the curve 62 of Figure 8 represents substantially the variations of sound intensity obtained with movement of the pedal 18. It will be seen that the rectilinear characteristics of this curve are opposed to those of the curve of W'ebers law given on page 18 of the James textbook above referred to and if averaged therewith, a substantially rectilinear or ideal curve would be produced, at least over a considerable range of intensities.

The invention upon which this application is based is broader than the specific embodiment shown and described for the purpose of illustrating at least one of the ways in which it may be employed. The scope of the invention is therefore to be understood as not being limited by the present specific description. I intend no limitations other than thos imposed by the claims.

lVhat is claimed is:

1. An instrument for producing damped compressional waves, comprising in combination a plurality of strings tuned to the notes of the musical scale, means for vibrating said strings by percussion, a casing surrounding sai strings, said casing having apertures, a plurality of pivotally mounted modulating reflectors for variably closing said apertures, each of said reflectors having its edge formed to restrict the emission of sound when the reflector is partially opened,

and a variable speed changing device "for operating said reflectors. v

2, An instrument for producing damped compressional waves, comprising in combination a plurality oi strings tuned to the notes of the musical scale, means "for vibrating said strings by percussion, a casing surrounding said strings, said casing having apertures, a plurality of pivotally mounted modulating reflectors tor variably closing said apertures, each of said reflectors having its edge formed to restrict the emission of sound when the reflector partially opened, and a variable speed mechanism :tor modifying the movement of said reflectors.

3. An instrument for producing compressional waves, comprising in nation a plurality of strings tuned to the notes of the musical scale, means for vibrating said strings by percussion, a casing surrounding said strings, said casing having apertures, a plurality pivotally mounted modulating reflectors 'ior variably closing said apertures, each said reil'lectors having its edge termed torestrict the emission oi sound when the reflector is partially opened, a control device arranged to be operated by the operators foot, and means interconnecting said pedal and said reflectors including a speed ratio modifying mechanism for translating constant movement of the control device into accelerating and decelerating movement of the reflectors.

4. In a musical instrument, the combination with means for producing musical sound by percussion, of casing having oppositely disposed controllable aoertures, modulating reflectors pivotal y mounted in said apertures for variably controlling and reflecting the sound emitted through said apertures, said reflectors having their contiguous edges formed to restrictthe emission of sound when the reflector is partially opened, a pedal arranged to be controlled by an operator, and a speed changing mechanism interconnecting the pedal and said reflectors for converting a constant speed of movement of the pedal into a variable speed movement of the reflectors.

5. In a musical instrument, the combination with means for producing musical sound by percussion, of a casing havig oppositely disposed controllable apertt. s, modulating reflectors pivotally mounted in said apertures for variably controlling and reflecting the sound emitted through said damped combiapeitures,said reflectors having their contiguous edges formed to restr'ct the emission of sound when the reflector is partially opened, a pedal arranged to be controlled by the operator, and a speed changing mechaiieetors for converting a constant speed of movemen of the pedal into a movement of the relatively slow when the reare partially opened.

a musical instrument, the combina tion with means for producing musical sound by percussion, eta casing surrounding said means and including a plurality of mov able sound controlling devices arranged to control the emission of sound, and operating mechanism for said sound control devices including speed changino means for varying the speed r opening or said control devices. T. In a musical inst ument, a plurality of tuned strings, a casing surrounding said s a plurality of movable reflectors positioned in said casing for controlling the emission of sound therefrom, a pedal, and means operatively interconnecting said pedal reflectors including variable speed and saio relatively slow movement of the reflectors when the reflectors are partially opened and to accelerate the movement of the reflectors as the extent of movement is increased.

8. ln musicalinstrument, the combination with a vibratory element for producing damped compressional waves, a casing therefor, a plurality of movable sound reflectors for controlling the emission of sound therefrom and formed to restrict the emission of sound when the reflectors are partially opened, and a variable speed mechanism arranged to accelerate the speed of opening of the reflectors substantially proportionally to the extent of opening provided thereby.

9. ln a musical instrument, the combina tion with a piano at a plurality of centrally pivoted reflectors for variably controlling sound, said reflectors having edges formed to restrict the emission of sound when the reflectors are partially opened, and a variable speed transmission mechanism for operating said reflectors,

Signed at New Yorlr'in the county of New York and State of New York this twenty fifth day of January A. D. 1926.

tercounecting the pedal and said re- 

